Fig. 6.

Endothelial cell Ca²⁺ increases in response to increasing K⁺ concentrations. A, representative trace illustrating endothelial cell Ca²⁺ response to incremental K⁺ concentrations measured by Fura-2 in control cells. B, summary data illustrating K⁺-dependent Ca²⁺ responses in endothelium from control and CH pulmonary arteries. KCl-induced Ca²⁺ responses were less at all K⁺ concentrations in cells from CH rats compared with controls. C, K⁺-induced Ca²⁺ influx was also performed in the presence of the K⁺-selective ionophore valinomycin (5 μM). Values are expressed as means ± S.E. (n = 4/group). P ≤ 0.05: *, versus control; **, versus 15 mM K⁺ concentration. D, summary data illustrating reduced Ca²⁺ entry after CH in response to 60 mM K⁺ and the effects of VGCC channel inhibition in control endothelial cells. Diltiazem (50 μM) and 10 μM mibefradil were used to selectively inhibit L-type and T-type VGCCs, respectively. ΔR is defined by change in F₃₄₀/F₃₈₀. Values are expressed as means ± S.E. (n = 4/group). P ≤ 0.05: *, versus control; **, versus control vehicle and control diltiazem.